nimbus-eth2/beacon_chain/validator_client/fork_service.nim

import common, api
import chronicles

logScope: service = "fork_service"

proc pollForFork(vc: ValidatorClientRef) {.async.} =
  let fork =
    try:
      await vc.getHeadStateFork()
    except ValidatorApiError as exc:
      error "Unable to retrieve head state's fork", reason = exc.msg
      return
    except CatchableError as exc:
      error "Unexpected error occured while getting fork information",
            err_name = exc.name, err_msg = exc.msg
      return

  if vc.fork.isNone() or vc.fork.get() != fork:
    vc.fork = some(fork)
    notice "Fork update success", fork = fork

proc waitForNextEpoch(service: ForkServiceRef) {.async.} =
  let vc = service.client
  let sleepTime = vc.beaconClock.durationToNextEpoch() + TIME_DELAY_FROM_SLOT
  debug "Sleeping until next epoch", sleep_time = sleepTime
  await sleepAsync(sleepTime)

proc mainLoop(service: ForkServiceRef) {.async.} =
  service.state = ServiceState.Running
  let vc = service.client
  debug "Service started"
  try:
    while true:
      await vc.pollForFork()
      await service.waitForNextEpoch()
  except CatchableError as exc:
    warn "Service crashed with unexpected error", err_name = exc.name,
         err_msg = exc.msg

proc init*(t: typedesc[ForkServiceRef],
            vc: ValidatorClientRef): Future[ForkServiceRef] {.async.} =
  debug "Initializing service"
  var res = ForkServiceRef(client: vc, state: ServiceState.Initialized)
  await vc.pollForFork()
  return res

proc start*(service: ForkServiceRef) =
  service.lifeFut = mainLoop(service)